Transcript Chapter 1.1

Chapter 1
Evolution
of
Communication Networks
Postacademic Interuniversity Course in Information Technology – Module C1
p1
Contents
• The 19th century telecommunications
– Telegraph - Telephone
– Digital vs. analog communications
• The voice networks & the data networks
• The electronics revolution (1960-1980)
– Digital sound
– Mainframe computers with remote access
– The first unification : ISDN
– Local area networks
– Wide area and local area networks integration
• The Internet
– The research project
– The universal computer communications medium
– The successful unification ?
Postacademic Interuniversity Course in Information Technology – Module C1
p2
Contents
• The 19th century telecommunications
– Telegraph - Telephone
– Digital vs. analog communications
• The voice networks & the data networks
• The electronics revolution (1960-1980)
– Digital sound
– Mainframe computers with remote access
– The first unification : ISDN
– Local area networks
– Wide area and local area networks integration
• The Internet
– The research project
– The universal computer communications medium
– The successful unification ?
Postacademic Interuniversity Course in Information Technology – Module C1
p3
The Chappe Telegraph
(Claude Chappe, 1763-1805)
92 out of
256 (= 4*8*8) positions
represented characters.
Integrity of message
could be restored at
each relay station
In 1844,
534 relays linked Paris
with 29 cities, covering
in total 5000 Km.
Postacademic Interuniversity Course in Information Technology – Module C1
p4
The Morse Telegraph
Samuel Morse, 1791-1872
First electrical
telegraph
demonstrated
in 1837
Postacademic Interuniversity Course in Information Technology – Module C1
p5
The Morse Telegraph
Signal strength can be restored by means of
electromechanical relays connecting separate
telegraphic circuits.
On land lines, unlimited distances can be
covered, without increasing significantly the
error rate.
Postacademic Interuniversity Course in Information Technology – Module C1
p6
The Telephone
Graham Bell, 1876.
Postacademic Interuniversity Course in Information Technology – Module C1
p7
Analog vs. Digital
6:12
Analog
• Almost infinite number of
states
• External perturbations can
not be distinguished from
original signal (superposed
noise)
• Information degrades along
the lines
Digital
• Finite, small, number of
states
• Most external perturbations
can be distinguished from
original signal
• Information can be restored
in relays
Postacademic Interuniversity Course in Information Technology – Module C1
p8
Digital Techniques
Representation of numbers in electronic devices ?
• Binary numbers (base 2) are used.
• A binary digit (bit) can be represented by a switch:
– Value 0 : switch open
– Value 1 : switch closed
• A number with n bits can take 2 n different values
– 2 bits :
4 combinations
– 3 bits :
–
–
–
–
00 01 10 11
8 combinations
000 001 010 011 100 101 110 111
8 bits (= 1 byte)
16 bits:
24 bits:
32 bits:
256 combinations
65 536 combinations
16 777 216 combinations
4 294 967 296 combinations
Postacademic Interuniversity Course in Information Technology – Module C1
p9
Contents
• The 19th century telecommunications
– Telegraph - Telephone
– Digital vs. analog communications
• The voice networks & the data networks
• The electronics revolution (1960-1980)
– Digital sound
– Mainframe computers with remote access
– The first unification : ISDN
– Local area networks
– Wide area and local area networks integration
• The Internet
– The research project
– The universal computer communications medium
– The successful unification ?
Postacademic Interuniversity Course in Information Technology – Module C1
p10
The Telephone
Full mesh network
n*(n-1)
2
Postacademic Interuniversity Course in Information Technology – Module C1
p11
The Telephone
With central switchboard
n
Postacademic Interuniversity Course in Information Technology – Module C1
p12
Automatic Exchange
(1920)
Conversation with
switch operator replaced
by signaling protocol
- Voice
: analog
- Signaling : digital
Postacademic Interuniversity Course in Information Technology – Module C1
p13
The Telephone Network
SW
SW
Trunk
lines
SW
SW
SW
SW
PABX
PABX
SW
Postacademic Interuniversity Course in Information Technology – Module C1
p14
Telex Networks
(1930-1990)
Morse code
replaced by
Baudot or
ASCII code
Postacademic Interuniversity Course in Information Technology – Module C1
p15
Alphabetical Codes
Morse
Baudot
ASCII
A
a
B
C
D
E
3
9
Postacademic Interuniversity Course in Information Technology – Module C1
p16
ASCII Character Set (7 bit)
000
nul 016
dle 032
048
0
064
@
080
P
096
`
112
p
001
soh 017
dc1 033
!
049
1
065
A
081
Q
097
a
113
q
002
stx 018
dc2 034
“
050
2
066
B
082
R
098
b
114
r
003
etx 019
dc3 035
#
051
3
067
C
083
S
099
c
115
s
004
eot 020
dc4 036
$
052
4
068
D
084
T
100
d
116
t
005
enq 021
nak 037
% 053
5
069
E
085
U
101
e
117
u
006
ack 022
syn 038
&
054
6
070
F
086
V
102
f
118
v
007
bel 023
etb 038
‘
055
7
071
G
087
W 103
g
119
w
008
bs
024
can 040
(
056
8
072
H
088
X
104
h
120
x
009
ht
025
em 041
)
057
9
073
I
089
Y
105
i
121
y
010
lf
026
sub 042
*
058
:
074
J
090
Z
106
j
122
z
011
vt
027
esc 043
+
059
;
075
K
091
[
107
k
123
k
012
ff
028
fs
044
,
060
<
076
L
092
\
108
l
124
{
013
cr
029
gs
045
-
061
=
077
M
093
]
109
m
125
|
014
so
030
rs
046
.
062
>
078
N
094
^
110
n
126
}
015
si
031
us
047
/
063
?
079
O
095
_
111
o
127
del
Postacademic Interuniversity Course in Information Technology – Module C1
p17
Unicode (16 bit)
0000
ASCII
Latin,Greek,Cyrillic, and Armenian
Arabic and Hebrew
Indic
Punctuation, math, graphics
Chinese / Japanese / Korean symbols
Unified Chinese / Japanese / Korean ideographs
Private applications
FFFF = 65537
Postacademic Interuniversity Course in Information Technology – Module C1
p18
The Dual Networks
Voice
Network
Analog+Digital
Data
Network
Digital
Postacademic Interuniversity Course in Information Technology – Module C1
p19
Contents
• The 19th century telecommunications
– Telegraph - Telephone
– Digital vs. analog communications
• The voice networks & the data networks
• The electronics revolution (1960-1980)
– Digital sound
– Mainframe computers with remote access
– The first unification : ISDN
– Local area networks
– Wide area and local area networks integration
• The Internet
– The research project
– The universal computer communications medium
– The successful unification ?
Postacademic Interuniversity Course in Information Technology – Module C1
p20
The Electronics Revolution
(1970-1980)
• Integrated circuits (“chips”) make electronics affordable.
• Mainframe computers become very powerful
• Mini & microcomputers become very popular
• Digital techniques offer better price/performance for
sound applications
Postacademic Interuniversity Course in Information Technology – Module C1
p21
Music Records
-096
+057
+164
+210
+219
+216
+165
-003
-117
-183
-138
-067
Analog
Postacademic Interuniversity Course in Information Technology – Module C1
Digital (CD)
(44100 measurements/s)
p22
Records with a scratch
-096
+057
+164
+210
XXXX
XXXX
XXXX
XXXX
-117
-183
-138
-067
Analog
Postacademic Interuniversity Course in Information Technology – Module C1
+210
+145
+079
+014
-052
-117
Digital (CD)
p23
Remote Computers Access
(1970)
Mainframe Computer
Star Network
Dumb Terminals
Postacademic Interuniversity Course in Information Technology – Module C1
p24
ISDN
The first attempt to integrate voice and data
• Integrated Services Digital Network
• Voice digitized at 64 Kb/s (8000 samples/s, 8 bit)
• Truly digital signaling
• A telephone connection = a 64 Kb/s digital link
+ A 64 Kb/s digital link is excellent for connecting a
terminal to a mainframe computer
- Connection time billing inadequate for data
ISDN widely used for telephony
ISDN marginal for data applications
Postacademic Interuniversity Course in Information Technology – Module C1
p25
Local Area Networks
(1970)
LAN’s initially introduced for
• Printer sharing
• File sharing
• ...
Postacademic Interuniversity Course in Information Technology – Module C1
p26
The Dual Screen Desk
(1980)
LAN
WAN
LAN
Postacademic Interuniversity Course in Information Technology – Module C1
p27
LAN-WAN Integration
(1990)
LAN
WAN
LAN
LAN
Postacademic Interuniversity Course in Information Technology – Module C1
p28
Client - Server Systems
Interconnection Network (LANs+WAN)
Postacademic Interuniversity Course in Information Technology – Module C1
p29
Client - Server Systems
Benefits
• Sharing of storage
– Access to common data
– Professional back-up facilities
– Centralized software (& data) maintenance
• Sharing of processing power
– Unloading of central servers
– Supporting local clients for exceptional needs
• Sharing of expensive peripherals
Postacademic Interuniversity Course in Information Technology – Module C1
p30
Terminal Emulation
= sub-minimal Client-server system
• The personal workstations are used
– as stand alone computers
– as terminals connected to other computers
• The user has to mentally switch between widely
different user interfaces and operating systems.
• Transferring data between local and remote
applications is far from trivial
• Terminal emulation is very user unfriendly !!!
Postacademic Interuniversity Course in Information Technology – Module C1
p31
Virtual Mainframe
= true Client-Server system
• The users interface of all applications runs on the
personal workstations.
• For some applications, the workstation requests help
from specialized servers. The user remains unaware
of such requests.
• Servers can be optimized for specific tasks
• Virtual Mainframes can be
– Very user friendly
– cost effective
Postacademic Interuniversity Course in Information Technology – Module C1
p32
Contents
• The 19th century telecommunications
– Telegraph - Telephone
– Digital vs. analog communications
• The voice networks & the data networks
• The electronics revolution (1960-1980)
– Digital sound
– Mainframe computers with remote access
– The first unification : ISDN
– Local area networks
– Wide area and local area networks integration
• The Internet
– The research project
– The universal computer communications medium
– The successful unification ?
Postacademic Interuniversity Course in Information Technology – Module C1
p33
70’s: Open Networks
CCITT/ISO start standardization work for
Open Systems Interconnection
ARPA finances Research on open Network Technology:
a Research WAN, ARPANET
research on LAN interconnections
Combination of the two ARPA efforts resulted in
the INTERNET
Postacademic Interuniversity Course in Information Technology – Module C1
p34
The Early ARPANET (1976)
London
Hawaii
56 Kbps terrestrial link
Satellite link
Postacademic Interuniversity Course in Information Technology – Module C1
p35
The Results:
• TCP/IP + Set of Application Protocols
– Set of communication “standards” allowing
interoperability of almost all brands of computers.
– Applicable to
• Local Area Networks
• Wide Area Networks
• Interconnection of LAN’s through WAN’s
• The INTERNET
– Communication facility for the Research Community
– Financed by US government
Postacademic Interuniversity Course in Information Technology – Module C1
p36
The success of TCP/IP
• To connect a computer to the ARPANET,
TCP/IP is required !
• Many different computers in use in Universities
and research centers.
• TCP/IP becomes THE networking software
available on ALL machines.
• Many stand-alone networks using TCP/IP
appear due to the wide availability of TCP/IP
and the many applications available for it.
Postacademic Interuniversity Course in Information Technology – Module C1
p37
The success ARPANET
•
•
•
•
– Universities where TCP/IP was developed
start using the ARPANET backbone as a
general purpose communication network.
Other universities and research centers also want to
get connected: with the help of the NSF, ARPANET
becomes the North American Research Network.
FREE access but “Acceptable Use Policy” imposed
by ARPA on all users.
Exponential growth of number of users
Enormous help for US researchers.
Postacademic Interuniversity Course in Information Technology – Module C1
p38
Major Internet Changes
1989-1992
• DARPA is no longer the major funds provider.
• Apparition of the .COM domain
• Backbone operated by private companies and paid
by the US-NSF and the connected networks.
• “Acceptable Use Policy” no longer required on the
backbone, even if many of the connected networks
still have one.
• Commercial “Internet Service Providers” build
private networks to connect their subscribers to the
Internet.
• The Internet has become a set of independently
financed, cooperating regional networks.
Postacademic Interuniversity Course in Information Technology – Module C1
p39
Internet Cost Structure
RARE
NL
USA
Surfnet
BE
Belnet
eunet
Planet
Planet
Uunet
Skynet
Uunet
• Backbone infrastructure and neutral
interconnects
• Paid by interconnected networks, proportional to
their access bandwidth.
• Cost of direct interconnects shared by partners.
• Not ACTUAL but POTENTIAL traffic is charged.
Postacademic Interuniversity Course in Information Technology – Module C1
p40
Firewalls
= Internet
= Firewall
= Intranet
= Secure Intranet
Postacademic Interuniversity Course in Information Technology – Module C1
p41
The Internet
Integration of voice & data services ???
• Internet has become almost as ubiquitous as the
traditional telephone network.
• Internet cost structure based upon potential usage
capabilities rather than actual usage.
• Larger and larger parts of the Internet have multi-media
capabilities.
• Talking over the Internet becomes a realistic low-cost
alternative to the traditional telephone service.
• Can the present Internet survive a victory over the
traditional telephone operators ???
• Will telephone operators themselves move their traffic to
the Internet ???
Postacademic Interuniversity Course in Information Technology – Module C1
p42
The Multi-media challenge
The notion of “Quality of Service”
Correctness:
Delay:
Data
Essential
Unimportant
Voice & Images
Non-essential
Small & Stable
Conclusion:
Data and multi-media traffic have
totally different requirements
Mixing them on a single network is
technically and economically challenging
Postacademic Interuniversity Course in Information Technology – Module C1
p43
Introduced concepts
• Digital vs. Analog communications
– Analog signals degraded by noise
– Digital signals can be restored to their original shape
– Different requirements for data and multi-media
• Data transmission and Signaling
– Signaling = management of the data transmission
• Client-server systems
• The Internet
– A set of protocols
– A set of interconnected networks
• Intranet
– Part of the Internet behind a firewall.
Postacademic Interuniversity Course in Information Technology – Module C1
p44